Proper treatment of diseases or medical conditions such as hepatitis C (HCV) frequently requires close monitoring of the amount of foreign materials, such as viral particles or pathogens, present in bodily fluids. The HCV virus present in the patient's blood, for example, is clinically referred to as the viral load and needs to be determined. Currently a blood sample is taken from the patient and viral particles are quantified, usually using PCR (Polymerase Chain Reaction) or TMA (Transcription Mediated Amplification) technology known in the art. Initial quantification of a patient's viral load can typically be obtained using commercially available tests because such patients typically have a sufficiently high viral load, one well within the detectable range of the most commonly used tests. Exemplary HCV detection tests may have a quantification range of approximately 108 viral particles to 172,000,000 viral particles per mL. Although more sensitive tests are available, these high sensitivity tests may have a small dynamic range and may be used in the limited cases when a physician knows a patient has a low viral load.
The number of particles that can be captured from a patient during testing is typically limited by the amount of bodily fluid that can be sampled. For example, physicians may sample between 1 mL and 3 mL of blood for each HCV test conducted. If the patient has a low level of viral particles in his or her blood, so low that a 3 mL blood draw may not contain any viral particles or a number insufficient for detection using PCR or TMA, then the test result will be undetectable (negative). These negative results can in many cases be classified as a false negative, because the patient is still infected but the viral level is too low to detect. Past improvements of HCV diagnostics have focused on enhancing the amplification methods in order to be able to detect lower concentrations of a virus in a traditional blood draw. While this has provided significant improvements for detecting the viral particles that are present in the sample, these traditional methods may still be ineffective, such as when the blood sample contains no viral particles.
Many HCV patients undergoing treatment will reach a point where current methods, even the most sensitive tests, may be insufficient to determine the true viral load. Some patients may achieve this undetectable level in only 4 weeks, or earlier, into a typical 48 week treatment. If a physician stops treatment in response to an undetectable result and a patient is still infected, then a patient may have a higher likelihood of relapsing than if treatment had been continued for the full term. Accordingly, physicians typically are forced to continue treatment for the clinically recommended length to avoid increasing the chance of relapse even if a patient may actually be cured. Furthermore, if the patient relapses, the viral infection may be harder to treat because the virus may be resistant to medication since it has already been exposed to treatment.
It would therefore be desirable to provide means and methods for accurately detecting and quantifying low viral loads or other materials that may affect patient health. It would also be desirable to provide an accurate quantification of such materials in order to determine whether the length of the patient's treatment may be shortened, thereby reducing the significant side-effects and costs associated with extended treatment.